5 files changed, 22 insertions, 4 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index da2f2f024a4d..a63bce8d0596 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -915,6 +915,8 @@ static void nfs_server_set_fsinfo(struct nfs_server *server, struct nfs_fsinfo *
 
         server->maxfilesize = fsinfo->maxfilesize;
 
+        server->time_delta = fsinfo->time_delta;
+
         /* We're airborne Set socket buffersize */
         rpc_setbufsize(server->client, server->wsize + 100, server->rsize + 100);
 }
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 39672b731736..c3f2477c16c1 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -758,6 +758,11 @@ do_unlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 }
 
 static int
+is_time_granular(struct timespec *ts) {
+        return ((ts->tv_sec == 0) && (ts->tv_nsec <= 1000));
+}
+
+static int
 do_setlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 {
         struct inode *inode = filp->f_mapping->host;
@@ -781,13 +786,21 @@ do_setlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
                 status = do_vfs_lock(filp, fl);
         if (status < 0)
                 goto out;
+
         /*
-         * Make sure we clear the cache whenever we try to get the lock.
+         * Revalidate the cache if the server has time stamps granular
+         * enough to detect subsecond changes.  Otherwise, clear the
+         * cache to prevent missing any changes.
+         *
          * This makes locking act as a cache coherency point.
          */
         nfs_sync_mapping(filp->f_mapping);
-        if (!nfs_have_delegation(inode, FMODE_READ))
-                nfs_zap_caches(inode);
+        if (!nfs_have_delegation(inode, FMODE_READ)) {
+                if (is_time_granular(&NFS_SERVER(inode)->time_delta))
+                        __nfs_revalidate_inode(NFS_SERVER(inode), inode);
+                else
+                        nfs_zap_caches(inode);
+        }
 out:
         return status;
 }
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index 31a44df40aea..d9a5e832c257 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -1044,8 +1044,9 @@ nfs3_xdr_fsinfores(struct rpc_rqst *req, __be32 *p, struct nfs_fsinfo *res)
         res->wtmult = ntohl(*p++);
         res->dtpref = ntohl(*p++);
         p = xdr_decode_hyper(p, &res->maxfilesize);
+        p = xdr_decode_time3(p, &res->time_delta);
 
-        /* ignore time_delta and properties */
+        /* ignore properties */
         res->lease_time = 0;
         return 0;
 }
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index c82ee7cd6288..5eef862ec187 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -124,6 +124,7 @@ struct nfs_server {
 
         struct nfs_fsid         fsid;
         __u64                   maxfilesize;    /* maximum file size */
+        struct timespec         time_delta;     /* smallest time granularity */
         unsigned long           mount_time;     /* when this fs was mounted */
         dev_t                   s_dev;          /* superblock dev numbers */
 
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index efe2eab8ac94..da7a1300dc60 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -112,6 +112,7 @@ struct nfs_fsinfo {
         __u32                   wtmult; /* writes should be multiple of this */
         __u32                   dtpref; /* pref. readdir transfer size */
         __u64                   maxfilesize;
+        struct timespec         time_delta; /* server time granularity */
         __u32                   lease_time; /* in seconds */
 };